Compact cable suspended pumping system for dewatering gas wells

ABSTRACT

A method of unloading liquid from a reservoir includes deploying a pumping system into a wellbore to a location proximate the reservoir using a cable. The pumping system includes a multi-section motor, an isolation device, and a pump. The method further includes supplying a power signal from the surface to the motor via the cable and sequentially operating each section of the motor to mimic a multi-phase motor, thereby driving the pump and lowering a liquid level in the tubular string to a level proximate the reservoir.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a compact cablesuspended pumping system for dewatering gas wells.

2. Description of the Related Art

As natural gas wells mature, many experience a decrease in productiondue to water build up in the annulus creating back pressure on thereservoir. The gas industry have utilized varying technologies toalleviate this problem, however most do not meet the economic hurdle asthey require intervention such as pulling the tubing string.

SUMMARY OF THE INVENTION

Embodiments of the present invention generally relate to a compact cablesuspended pumping system for dewatering gas wells. In one embodiment, amethod of unloading liquid from a reservoir includes deploying a pumpingsystem into a wellbore to a location proximate the reservoir using acable. The pumping system includes a multi-section motor, an isolationdevice, and a pump. The method further includes supplying a power signalfrom the surface to the motor via the cable and sequentially operatingeach section of the motor to mimic a multi-phase motor, thereby drivingthe pump and lowering a liquid level in the tubular string to a levelproximate the reservoir.

In another embodiment, a pumping system includes a submersiblemulti-section electric motor operable to rotate a drive shaft. Eachsection is incrementally oriented so that the sections are operable tomimic a multi-phase motor. The pumping system further includes a pumprotationally connected to the drive shaft; an isolation device operableto engage a tubular string, thereby fluidly isolating an inlet of thepump from an outlet of the pump and rotationally connecting the motorand the pump to the tubular string; and a cable having two or lessconductors, a strength sufficient to support the motor, the pump, andthe isolation device, and in electrical communication with the motor.

In another embodiment, a motor includes two or more sections. Eachsection includes a submersible tubular housing and a stator coredisposed within the housing. The stator core has one or more lobes andeach lobe has a winding wrapped therearound. The motor further includesa rotor disposed within the housing and including a shaft and a rotorcore. The rotor core has two or more lobes. Each section isincrementally oriented so that the sections may be operated to mimic amulti-phase motor.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1A illustrates a pumping system, such as an electric submersiblepumping system, deployed in a wellbore, according to one embodiment ofthe present invention. FIG. 1B illustrates an electric submersiblepumping system deployed in a wellbore, according to another embodimentof the present invention.

FIG. 2A is a layered view of the power cable. FIG. 2B is an end view ofthe power cable.

FIG. 3A is an external view of the motor minus the housing. FIG. 3B isan enlargement of a portion of FIG. 3A. FIG. 3C is a schematic of themulti-section motor mimicking operation of a multi-phase motor. FIG. 3Dis a cross section of the stator. FIG. 3E is a cross section of therotor.

FIG. 4A is a cross-section of a stage of the pump. FIG. 4B is anexternal view of a mandrel of the pump stage.

DETAILED DESCRIPTION

FIG. 1A illustrates a pumping system, such as an electric submersiblepumping system (ESP) 1, deployed in a wellbore 5, according to oneembodiment of the present invention. The wellbore 5 has been drilledfrom a surface of the earth 20 or floor of the sea (not shown) into ahydrocarbon-bearing (i.e., natural gas 100 g) reservoir 25. A string ofcasing 10 c has been run into the wellbore 5 and set therein with cement(not shown). The casing 10 c has been perforated 30 to provide toprovide fluid communication between the reservoir 25 and a bore of thecasing 10. A wellhead 15 has been mounted on an end of the casing string10 c. An outlet line 35 extends from the wellhead 15 to productionequipment (not shown), such as a separator. A production tubing string10 t has been run into the wellbore 5 and hung from the wellhead 15. Aproduction packer 85 has been set to isolate an annulus between thetubing 10 t and the casing 10 c from the reservoir 25. The reservoir 25may be self-producing until a pressure of the gas 100 g is no longersufficient to transport a liquid, such as water 100 w, to the surface. Alevel of the water 100 w begins to build in the production tubing 10 t,thereby exerting hydrostatic pressure on the reservoir 25 anddiminishing flow of gas 100 g from the reservoir 25.

FIG. 1B illustrates the ESP 1 deployed in a wellbore 5, according toanother embodiment of the present invention. In this embodiment, thecasing 10 c has been used to produce fluid from the reservoir 25 insteadof installing production tubing. In this scenario, the isolation device70 may be set against the casing 10 c and the pump 65 may discharge thewater 100 w to the surface 20 via a bore of the casing 10 c.

The ESP 1 may include a surface controller 45, an electric motor 50, apower conversion module (PCM) 55, a seal section 60, a pump 65, anisolation device 70, a cablehead 75, and a power cable 80. Housings ofeach of the downhole components 50-75 may be longitudinally androtationally connected, such as with flanged or threaded connections.The downhole component housings may be made from a corrosion resistantmetal or alloy, such as galvanized steel, stainless steel, or a nickelbased alloy. Since the downhole components 50-75 may be deployed withinthe tubing 10 t, the components 50-80 may be compact, such as having amaximum outer diameter less than or equal to two or one andthree-quarter inches (depending on the inner diameter of the tubing 10t).

The surface controller 45 may be in electrical communication with analternating current (AC) power source 40, such as a generator on aworkover rig (not shown). The surface controller 45 may include atransformer (not shown) for stepping the voltage of the AC power signalfrom the power source 40 to a medium voltage (V) signal. The mediumvoltage may be greater than or equal to one kV, such as five to ten kV.The surface controller may further include a rectifier for convertingthe medium voltage AC signal to a medium voltage direct current (DC)power signal for transmission downhole via the power cable 80. Thesurface controller 45 may further include a data modem (not shown) and amultiplexer (not shown) for modulating and multiplexing a data signalto/from the PCM 55 with the DC power signal. The surface controller 45may further include an operator interface (not shown), such as avideo-display, touch screen, and/or USB port.

The cable 80 may extend from the surface controller 45 through thewellhead 15 or connect to leads which extend through the wellhead 15 andto the surface controller 45. The cable 80 may be received by slips or aclamp (not shown) disposed in or proximate to the wellhead 15 forlongitudinally connecting the cable 80 to the wellhead 15 duringoperation of the ESP 1. The cable 80 may extend into the wellbore 5 tothe cablehead 75. Since the power signal may be DC, the cable 80 mayonly include two conductors arranged coaxially.

FIG. 2A is a layered view of the power cable 80. FIG. 2B is an end viewof the power cable 80. The cable 80 may include an inner core 205, aninner jacket 210, a shield 215, an outer jacket 230, and armor 235, 240.The inner core 205 may be the first conductor and made from anelectrically conductive material, such as aluminum, copper, aluminumalloy, or copper alloy. The inner core 205 may be solid or stranded. Theinner jacket 210 may electrically isolate the core 205 from the shield215 and be made from a dielectric material, such as a polymer (i.e., anelastomer or thermoplastic). The shield 215 may serve as the secondconductor and be made from the electrically conductive material. Theshield 215 may be tubular, braided, or a foil covered by a braid. Theouter jacket 230 may electrically isolate the shield 215 from the armor235, 240 and be made from an oil-resistant dielectric material. Thearmor may be made from one or more layers 235, 240 of high strengthmaterial (i.e., tensile strength greater than or equal to two hundredkpsi) to support the deployment weight (weight of the cable and theweight of the downhole components 50-75) so that the cable 80 may beused to deploy and remove the downhole components 50-75 into/from thewellbore 5. The high strength material may be a metal or alloy andcorrosion resistant, such as galvanized steel, stainless steel, or anickel alloy depending on the corrosiveness of the gas 100 g. The armormay include two contra-helically wound layers 235, 240 of wire or strip.

Additionally, the cable 80 may include a sheath 225 disposed between theshield 215 and the outer jacket 230. The sheath 225 may be made fromlubricative material, such as polytetrafluoroethylene (PTFE) or lead andmay be tape helically wound around the shield 215. If lead is used forthe sheath, a layer of bedding 220 may insulate the shield 215 from thesheath and be made from the dielectric material. Additionally, a buffer245 may be disposed between the armor layers 235, 240. The buffer 245may be tape and may be made from the lubricative material.

Due to the coaxial arrangement, the cable 80 may have an outer diameter250 less than or equal to one and one-quarter inches, one inch, orthree-quarters of an inch.

Additionally, the cable 80 may further include a pressure containmentlayer (not shown) made from a material having sufficient strength tocontain radial thermal expansion of the dielectric layers and wound toallow longitudinal expansion thereof. The material may be stainlesssteel and may be strip or wire. Alternatively, the cable 80 may includeonly one conductor and the tubing 10 t may be used for the otherconductor.

The cable 80 may be longitudinally connected to the cablehead 75. Thecablehead 75 may also include leads (not shown) extending therethrough.The leads may provide electrical communication between the conductors ofthe cable 80 and the PCM 55.

FIG. 3A is an external view of the motor 50 minus the housing. FIG. 3Bis an enlargement of a portion of FIG. 3A. FIG. 3C is a schematic of themulti-section motor 50 mimicking operation of a multi-phase motor. FIG.3D is a cross section of the stator 110 s. FIG. 3E is a cross section ofthe rotor 110 r.

The motor 50 may be filled with a dielectric, thermally conductiveliquid lubricant, such as mineral oil. The motor 50 may be cooled bythermal communication with the reservoir water 100 w. The motor 50 mayinclude a thrust bearing (not shown) for supporting a drive shaft 135.In operation, the motor 50 may rotate the shaft 135, thereby driving thepump 65. The motor shaft 135 may be directly (no gearbox) connected to arotor 160 of the pump via a shaft of the motor seal 60. As discussedabove, since the motor 50 may be compact, the motor may operate at highspeed so that the pump may generate the necessary head to pump the water100 w to the surface 20. High speed may be greater than or equal to tenor fifteen thousand revolutions per minute (RPM).

The motor 50 may include two or more sections 105 a-c, 106 a -c. Eachsection 105 a-c, 106 a-c may include a rotor 110 r and a stator 110 s.The stator 110 s may include the housing 115, a core 120 s, windings125, and leads 130. The housing 115 may be tubular and have a boretherethrough. Each section 105 a-c, 106 a-c may be longitudinally androtationally connected, such as by flanges or threads (not shown). Thecore 120 s may include one or more lobes 121 (two shown). Each lobe 121may be wound and the windings 125 of opposing lobes 121 may be connected(not shown) in series or parallel to define a phase. The motor 50 mayfurther include one or more sets, such as a first set 105 and a secondset 106 (not shown) of sections 105 a-c, 106 a -c. The stator 110 s ofeach section 105 a-c, 106 a-c of each set 105, 106 may be incrementallyoriented relative to each other based on a three-hundred and sixtydegree sum. For example, for three sections, each section 105 a-c, 106a-c may be shifted by one-hundred twenty degrees relative to othersections of the set. Alternatively, each rotor 110 r of each section 105a-c, 106 a-c of each set 105, 106 may be shifted instead of shifting thestators 110 s.

Each section 105 a-c, 106 a-c may be electrically connected to the PCM55 by the leads 130. Respective sections (i.e., 105 a, 106 a ) of eachset 105, 106 may correspond, thereby operating as a single phase. Thecorresponding sections of the sets 105, 106 may be electricallyconnected to the PCM 55 in parallel or series. Shifted sections (i.e.,105 a, b) of each set 105, 106 may be connected to the PCM 55 inparallel. Each set 105, 106 may be controlled by the PCM 55 to mimic oneor more multi-phase motors 105 e (may be viewed as a single motor or twomotors in series), such as a three-phase (six stator lobes) motor. Otherthan for the orientation, each of the sections 105 a-c, 106 a-c may beidentical, thereby forming a modular motor 50.

The motor 50 may be a switched reluctance motor (SRM). Each rotor 110 rmay include a shaft 135 and a core 120 r. The shaft 135 may be made froma metal or alloy, such as plain carbon or low alloy steel, stainlesssteel, or a nickel based alloy. The core 120 r may have two or morelobes 122, such as four, each spaced apart by ninety degree increments.Each of the cores 120 s, 120 r may be laminates. Each layer of thelaminates may be made from a metal or alloy, such as silicon steel. Thelayers may be aligned and then pressed together to form one of the cores120 r,s. The windings 125 may then be wrapped around each lobe 121. Thestator core 120 s may be longitudinally and rotationally connected tothe housing 115, such as by a key and keyway (not shown) and fasteners.The housing 115 may include an external indicator (not shown), such as agroove or protrusion, to facilitate orientation of the sections 105 a-c,106 a-c with respect to one another. The rotor core 120 r may belongitudinally and rotationally connected to the shaft 135, such as by akey, keyway, and fasteners or an interference fit. Each of the leads 130and windings 125 may include a core made from an electrically conductivematerial, as discussed above, and be jacketed by a dielectric material,as discussed above.

Each section 105 a-c, 106 a-c may further include a bearing 140, such asa radial bearing, for supporting rotation of the shaft 135 relative tothe housing 115. The bearing 140 may be a rolling element bearing, suchas a ball bearing. The bearing 140 may include a gland 141 housing anouter race 142 s. The gland 141 may be connected (not shown) to thehousing 115 and the outer race 142 s connected to the gland 141. Thebearing 140 may further include an inner race 142 r connected to theshaft 135. Balls 143 (schematically shown) may be disposed between theraces 142 r,s and lubricant may be sealed within the races.Alternatively, the bearing 140 may be a hydrodynamic bearing, asdiscussed below.

The PCM 55 may include a motor controller (not shown), a modem (notshown), and demultiplexer (not shown). The modem and demultiplexer maydemultiplex a data signal from the DC power signal, demodulate thesignal, and transmit the data signal to the motor controller. The motorcontroller may receive the medium voltage DC signal from the cable andsequentially energize the shifted sections 105 a-c (& 106 a-c) of themotor 50, thereby supplying an output signal to drive the particularsection of the motor and coordinating operation of each set of sectionsas a multi-phase motor. The output signal may be stepped, trapezoidal,or sinusoidal. The motor controller may include a logic circuit forsimple control (i.e. predetermined speed) or a microprocessor forcomplex control (i.e., variable speed drive and/or soft startcapability). The motor controller may use one or two-phase excitation,be unipolar or bi-polar, and control the speed of the motor bycontrolling the switching frequency. The motor controller may include anasymmetric bridge or half-bridge.

Alternatively, the motor 50 may be permanent magnet motor, such as abrushless DC motor (BLDC) made in a similar multi-section fashion. TheBLDC motor may include three shifted stator sections to mimic a threephase (two pole) winding, a permanent magnet rotor, and a rotor positionsensor. The permanent magnet rotor may be made of a rare earth magnet ora ceramic magnet. The rotor position sensor may be a Hall-effect sensor,a rotary encoder, or sensorless (i.e., measurement of back EMF inundriven coils by the motor controller). The BLDC motor controller maybe in communication with the rotor position sensor and include a bank oftransistors or thyristors and a chopper drive for complex control (i.e.,variable speed drive and/or soft start capability).

Additionally, the PCM 55 may include a power supply (not shown). Thepower supply may include one or more DC/DC converters, each converterincluding an inverter, a transformer, and a rectifier for converting theDC power signal into an AC power signal and stepping the voltage frommedium to low, such as less than or equal to one kV. The power supplymay include multiple DC/DC converters in series to gradually step the DCvoltage from medium to low. The low voltage DC signal may then besupplied to the motor controller.

The motor controller may be in data communication with one or moresensors (not shown) distributed throughout the downhole components50-75. A pressure and temperature (PT) sensor may be in fluidcommunication with the water 100 w entering the intake 65 i. A gas toliquid ratio (GLR) sensor may be in fluid communication with the water100 w entering the intake 65 i. A second PT sensor may be in fluidcommunication with the water 100 w discharged from the outlet 650. Atemperature sensor (or PT sensor) may be in fluid communication with thelubricant to ensure that the motor and downhole controller are beingsufficiently cooled. Multiple temperature sensors may be included in thePCM 55 for monitoring and recording temperatures of the variouselectronic components. A voltage meter and current (VAMP) sensor may bein electrical communication with the cable 80 to monitor power loss fromthe cable. A second VAMP sensor may be in electrical communication withthe motor controller output to monitor performance of the motorcontroller. Further, one or more vibration sensors may monitor operationof the motor 50, the pump 65, and/or the seal section 60. A flow metermay be in fluid communication with the discharge 65 o for monitoring aflow rate of the pump 65. Utilizing data from the sensors, the motorcontroller may monitor for adverse conditions, such as pump-off, gaslock, or abnormal power performance and take remedial action beforedamage to the pump 65 and/or motor 50 occurs.

The seal section 60 may isolate the water 100 w being pumped through thepump 65 from the lubricant in the motor 50 by equalizing the lubricantpressure with the pressure of the water 100 w. The seal section 60 mayrotationally connect the motor shaft 135 to a drive shaft of the pump65. The shaft seal may house a thrust bearing capable of supportingthrust load from the pump 65. The seal section 60 may be positive typeor labyrinth type. The positive type may include an elastic,fluid-barrier bag to allow for thermal expansion of the motor lubricantduring operation. The labyrinth type may include tube paths extendingbetween a lubricant chamber and a water chamber providing limited fluidcommunication between the chambers.

The pump may include an inlet 65 i. The inlet 65 i may be standard type,static gas separator type, or rotary gas separator type depending on theGLR of the reservoir fluid. The standard type intake may include aplurality of ports allowing water 100 w to enter a lower or first stageof the pump 65. The standard intake may include a screen to filterparticulates from the water 100 w. The static gas separator type mayinclude a reverse-flow path to separate a gas portion of the reservoirfluid from a liquid portion of the reservoir fluid.

FIG. 4A is a cross-section of a stage 65 s of the pump 65. FIG. 4B is anexternal view of a mandrel 155 of the pump stage 65 s. The pump 65 mayinclude one or more stages 65 s, such as six. Each stage 65 s may belongitudinally and rotationally connected, such as with threadedcouplings or flanges (not shown). Each stage 65 s may include a housing150, a mandrel 155, and an annular passage 170 formed between thehousing and the mandrel. The housing 150 may be tubular and have a boretherethrough. The mandrel 155 may be disposed in the housing 150. Themandrel 155 may include a rotor 160, one or more helicoidal rotor vanes160 a,b, a diffuser 165, and one or more diffuser vanes 165 v. The rotor160, housing 155, and diffuser 165 may each be made from a metal, alloy,or cermet corrosion and erosion resistant to the production fluid, suchas steel, stainless steel, or a specialty alloy, such aschrome-nickel-molybdenum. Alternatively, the rotor, housing, anddiffuser may be surface-hardened or coated to resist erosion.

The rotor 160 may include a shaft portion 160 s and an impeller portion160 i. The portions 160 i,s may be integrally formed. Alternatively, theportions 160 i,s may be separately formed and longitudinally androtationally connected, such as by a threaded connection. The rotor 160may be supported from the diffuser 165 for rotation relative to thediffuser and the housing 150 by a hydrodynamic radial bearing (notshown) formed between an inner surface of the diffuser and an outersurface of the shaft portion 160 s. The radial bearing may utilizeproduction fluid or may be isolated from the production fluid by one ormore dynamic seals, such as mechanical seals, controlled gap seals, orlabyrinth seals. The diffuser 165 may be solid or hollow. If thediffuser is hollow, it may serve as a lubricant reservoir in fluidcommunication with the hydrodynamic bearing. Alternatively, one or morerolling element bearings, such as ball bearings (see bearing 140,discussed above), may be disposed between the diffuser 165 and shaftportion 160 s instead of the hydrodynamic bearings.

The rotor vanes 160 a,b may be formed with the rotor 160 and extend froman outer surface thereof or be disposed along and around an outersurface thereof. Alternatively the rotor vanes 160 a,b may be depositedon an outer surface of the rotor after the rotor is formed, such as byspraying or weld-forming. The rotor vanes 160 a,b may interweave to forma pumping cavity therebetween. A pitch of the pumping cavity mayincrease from an inlet 170 i of the stage 65 s to an outlet 1700 of thestage. The rotor 160 may be longitudinally and rotationally coupled tothe motor drive shaft and be rotated by operation of the motor. As therotor is rotated, the water 100 w may be pumped along the cavity fromthe inlet 170 i toward the outlet 1700.

An outer diameter of the impeller 160 i may increase from the inlet 170i toward the outlet 170 o in a curved fashion until the impeller outerdiameter corresponds to an outer diameter of the diffuser 165. An innerdiameter of the housing 150 facing the impeller portion 160 i mayincrease from the inlet 170 i to the outlet 170 o and the housing innersurface may converge toward the impeller outer surface, therebydecreasing an area of the passage 170 and forming a nozzle 170 n. As thewater 100 w is forced through the nozzle 170 n by the rotor vanes 160a,b, a velocity of the water 100 w may be increased.

The stator may include the housing 150 and the diffuser 165. Thediffuser 165 may be formed integrally with or separately from thehousing 150. The diffuser 165 may be tubular and have a boretherethrough. The rotor 160 may have a shoulder between the impeller 160i and shaft 160 s portions facing an end of the diffuser 165. The shaftportion 160 s may extend through the diffuser 165. The diffuser 165 maybe longitudinally and rotationally connected to the housing 150 by oneor more ribs. An outer diameter of the diffuser 165 and an innerdiameter of the housing 150 may remain constant, thereby forming athroat 170 t of the passage 170. The diffuser vanes 165 v may be formedwith the diffuser 165 and extend from an outer surface thereof or bedisposed along and around an outer surface thereof. Alternatively thediffuser vanes 165 v may be deposited on an outer surface of thediffuser after the diffuser is formed, such as by spraying orweld-forming. Each diffuser vane 165 v may extend along an outer surfaceof the diffuser 165 and curve around a substantial portion of thecircumference thereof. Cumulatively, the diffuser vanes 165 v may extendaround the entire circumference of the diffuser 165. The diffuser vanes165 v may be oriented to negate swirl in the flow of water 100 w causedby the rotor vanes 160 a,b, thereby minimizing energy loss due toturbulent flow of the water 100 w. In other words, the diffuser vanes165 v may serve as a vortex breaker. Alternatively, a single helicaldiffuser vane may be used instead of a plurality of diffuser vanes 165v.

An outer diameter of the diffuser 165 may decrease away from the inlet170 i to the outlet 170 o in a curved fashion until an end of thediffuser 165 is reached and an outer surface of the shaft portion 160 sis exposed to the passage 170. An inner diameter of the housing 150facing the diffuser 165 may decrease away from the inlet 170 i to theoutlet 170 o and the housing inner surface may diverge from the diffuserouter surface, thereby increasing an area of the passage 170 and forminga diffuser 170 d. As the water 100 w flows through the diffuser 170 d, avelocity of the water 100 w may be decreased. Inclusion of the Venturi170 n,t,d may also minimize fluid energy loss in the water dischargedfrom the rotor vanes 160 a,b.

As discussed above, for compactness, the motor 50 and pump 65 mayoperate at the high speed so that the compact pump 65 may generate thenecessary head to pump the water 100 w to the outlet line 35 whileminimizing a diameter thereof.

The isolation device 70 may include a packer, an anchor, and anactuator. The actuator may include a brake, a cam, and a cam follower.The packer may be made from a polymer, such as a thermoplastic orelastomer, such as rubber, polyurethane, or PTFE. The cam may have aprofile, such as a J-slot and the cam follower may include a pin engagedwith the J-slot. The anchor may include one or more sets of slips, andone or more respective cones. The slips may engage the production tubing10 t, thereby rotationally connecting the downhole components 50-75 tothe production tubing. The slips may also longitudinally support thedownhole components 50-75. The brake and the cam follower may belongitudinally connected and may also be rotationally connected. Thebrake may engage the production tubing 10 t as the downhole components50-75 are being run-into the wellbore. The brake may include bow springsfor engaging the production tubing. Once the downhole components 50-75have reached deployment depth, the cable 80 may be raised, therebycausing the cam follower to shift from a run-in position to a deploymentposition. The cable 80 may then be relaxed, thereby, causing the weightof the downhole components 50-75 to compress the packer and the slipsand the respective cones, thereby engaging the packer and the slips withthe production tubing 10 t. The isolation device 70 may then be releasedby pulling on the cable 80, thereby again shifting the cam follower to arelease position. Continued pulling on the cable 80 may release thepacker and the slips, thereby freeing the downhole components 50-75 fromthe production tubing 10 t.

Alternatively, the actuator may include a piston and a control valve.Once the downhole components 50-75 have reached deployment depth, themotor 50 and pump 65 may be activated. The control valve may remainclosed until the pump exerts a predetermined pressure on the valve. Thepredetermined pressure may cause the piston to compress the packer andthe slips and cones, thereby engaging the packer and the slips with theproduction tubing. The valve may further include a vent to releasepressure from the piston once pumping has ceased, thereby freeing theslips and the packer from the production tubing. Additionally, theactuator may further be configured so that relaxation of the cable 80also exerts weight to further compress the packer, slips, and cones andrelease of the slips may further include exerting tension on the cable80.

Additionally, the isolation device 70 may include a bypass vent (notshown) for releasing gas separated by the inlet 65 i that may collectbelow the isolation device and preventing gas lock of the pump 65. Apressure relief valve (not shown) may be disposed in the bypass vent.Additionally, a downhole tractor (not shown) may be integrated into thecable 80 to facilitate the delivery of the downhole components 50-75,especially for highly deviated wells, such as those having aninclination of more than forty-five degrees or dogleg severity in excessof five degrees per one hundred feet. The drive and wheels of thetractor may be collapsed against the cable and deployed when required bya signal from the surface.

In operation, to install the ESP 1, a workover rig (not shown) and theESP 1 may be deployed to the wellsite. Since the cable 80 may includeonly two conductors, the cable 80 may be delivered wound onto a drum(not shown). The wellhead 15 may be opened. The components 50-75 may besuspended over the wellbore 5 from the workover rig and an end of thecable 80 may be connected to the cablehead 75. The cable 80 may beunwound from the drum, thereby lowering the downhole components 50-75into the wellbore 5 inside of the production tubing 10 t. Once thedownhole components 50-75 have reached the desired depth proximate tothe reservoir 25, the wellhead 15 may be closed and the conductors ofthe cable 80 may be connected to the surface controller 45.

The isolation device 70 may then be set. Once the isolation device 70 isset, the motor 50 may then be started (if not already started to set theisolation device). If the motor controller is variable, the motorcontroller may soft start the motor 50. As the pump 65 is operating, themotor controller may send data from the sensors to the surface so thatthe operator may monitor performance of the pump. If the motorcontroller is variable, a speed of the motor 50 may be adjusted tooptimize performance of the pump 65. Alternatively, the surface operatormay instruct the motor controller to vary operation of the motor. Thepump 65 may pump the water 100 w through the production tubing 10 t andthe wellhead 15 into the outlet 35, thereby lowering a level of thewater 100 w and reducing hydrostatic pressure of the water 100 w on theformation 25. The pump 65 may be operated until the water level islowered to the inlet 65 i of the pump, thereby allowing naturalproduction from the reservoir 25. The operator may then sendinstructions to the motor controller to shut down the pump 65 or simplycut power to the cable 80. The isolation device 70 may then be unset (ifnot unset by shutdown of the pump) by winding the drum to exertsufficient tension in the cable 80. The cable 80 may be wound, therebyraising the downhole components 50-75 from the wellbore 5. The workoverrig and the ESP 1 may then be redeployed to another wellsite.

Advantageously, deployment of the downhole components 50-75 using thecable 80 inside of the production tubing 10 t instead of removing theproduction tubing string and redeploying the production tubing stringwith a permanently mounted artificial lift system reduces the requiredsize of the workover rig and the capital commitment to the well.Deployment and removal of the ESP 1 to/from the wellsite may beaccomplished in a matter of hours, thereby allowing multiple wells to bedewatered in a single day. Transmitting a DC power signal through thecable 80 reduces the required diameter of the cable, thereby allowing alonger length of the cable 80 (i.e., five thousand to eight thousandfeet) to be spooled onto a drum, and easing deployment of the cable 80.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of unloading liquid from a reservoir, comprising: deployinga pumping system into a wellbore to a location proximate the reservoirusing a cable, wherein the pumping system comprises a multi-sectionmotor, an isolation device, and a pump; and supplying a power signalfrom the surface to the motor via the cable and sequentially operatingeach section of the motor to mimic a multi-phase motor, thereby drivingthe pump and lowering a liquid level in the tubular string to a levelproximate the reservoir.
 2. The method of claim 1, further comprisingsetting the isolation device before or as a result of supplying thepower signal, thereby rotationally connecting the pumping system to atubular string disposed in the wellbore and isolating an inlet of thepump from an outlet of the pump.
 3. The method of claim 1, furthercomprising: ceasing supply of the power signal; unsetting the isolationdevice after or as a result of ceasing the power signal supply; andremoving the pumping system from the wellbore using the cable.
 4. Themethod of claim 1, wherein: the power signal is medium voltage DC viathe cable, the pumping assembly further comprises a power conversionmodule (PCM), and the PCM outputs a low voltage signal to the motor. 5.The method of claim 1, wherein motor and the pump are operated atgreater than or equal to ten thousand RPM.
 6. The method of claim 1,wherein a maximum outer diameter of the pump assembly and the cable isless than or equal to two inches.
 7. The method of claim 1, furthercomprising controlling a speed of the motor.
 8. The method of claim 1,wherein: the pumping system comprises a sensor, and the method furthercomprises transmitting a measurement by the sensor to the surface viathe cable.
 9. The method of claim 1, wherein the isolation devicelongitudinally connects the pumping system to the tubular string,thereby supporting a weight of the tubular string.
 10. A pumping system,comprising: a submersible multi-section electric motor operable torotate a drive shaft, wherein each section is incrementally oriented sothat the sections are operable to mimic a multi-phase motor; a pumprotationally connected to the drive shaft; an isolation device operableto engage a tubular string, thereby fluidly isolating an inlet of thepump from an outlet of the pump and rotationally connecting the motorand the pump to the tubular string; and a cable having two or lessconductors, a strength sufficient to support the motor, the pump, andthe isolation device, and in electrical communication with the motor.11. The pumping system of claim 10, wherein a maximum outer diameter ofthe motor, pump, isolation device, and cable is less than or equal totwo inches.
 12. The pumping system of claim 10, further comprising apower conversion module (PCM) operable to: receive a medium voltage DCpower signal from the cable, and supply a low voltage power signal tothe motor.
 13. The pumping system of claim 12, wherein the PCM isoperable to vary a speed of the motor.
 14. The pumping system of claim10, wherein the motor is a switched reluctance motor.
 15. The pumpingsystem of claim 10, wherein the motor and the pump are operable atgreater than or equal to ten thousand RPM.
 16. The pumping system ofclaim 10, further comprising: a sensor; and a modem operable to send ameasurement from the sensor along the cable.
 17. The pumping system ofclaim 10, wherein the isolation device is further operable to supportthe weight of the motor, the pump, and the isolation device.
 18. Thepumping system of claim 10, wherein each section comprises: asubmersible tubular housing; a stator core disposed within the housingand having one or more lobes, each lobe having a winding wrappedtherearound; and a rotor disposed within the housing and comprising ashaft and a rotor core, the rotor core having two or more lobes.
 19. Thepumping system of claim 10, wherein the pump further comprises one ormore stages, each stage comprising: a tubular housing; a mandreldisposed in the housing and comprising: the rotor rotatable relative tothe housing and having: an impeller portion, a shaft portion, thehelicoidal vanes extending along the impeller portion, a diffuser:connected to the housing, having the shaft portion extendingtherethrough, and having one or more vanes operable to negate swirlimparted to fluid pumped through the impeller portion; and a fluidpassage formed between the housing and the mandrel and having a nozzlesection, a throat section, and a diffuser section.
 20. A motorcomprising two or more sections, each section comprising: a submersibletubular housing; a stator core disposed within the housing and havingone or more lobes, each lobe having a winding wrapped therearound; and arotor disposed within the housing and comprising a shaft and a rotorcore, the rotor core having two or more lobes, wherein each section isincrementally oriented so that the sections may be operated to mimic amulti-phase motor.